Conventional microwave ovens are generally classified into several different types including: tabletop microwave ovens designed to be seated on a table and/or countertop; and a ventilation hood-combined microwave oven designed to be mounted above a oven range—sometimes referred to as Over-The-Range (OTR) microwaves. An OTR microwave includes a ventilation hood type system for exhausting hot air, steam, smoke, etc. generated from the oven range. The ventilation system for a typical OTR microwave normally includes a suction opening, which is frequently provided with a grease/smoke filter, located along the bottom surface of the OTR microwave. Exhaust air flow is drawn into the suction opening and is passed around the microwave oven cavity and is directed either back into the kitchen environment through an exhaust outlet opening or is directed to an external exhaust.
U.S. Pat. No. 4,327,274 discloses an OTR microwave having a bottom vent openings provided with air intake filters wherein a blower draws exhaust air in through the vent openings and directs the exhaust air through a passage between the back wall of the microwave cavity and a rear cabinet wall. The exhaust air then exits the microwave assembly through either a top or rear outlet opening, depending on the installation configuration.
U.S. Patent Application 2003/0218011 A1 discloses a wall mounted microwave oven having an exhaust fan assembly which is mounted above and behind the cooking chamber. By changing the orientation of the fan case, the exhaust air may be directed upwardly, rearwardly or forwardly. In the forward direction, the exhaust gas is discharged forwardly into the room and may pass through a filter unit (not shown).
U.S. Pat. No. 6,621,057 discloses a OTR microwave having an exhaust fan located above the cooking chamber and to the rear of the cooking chamber. The exhaust fan system, including a motor and fans, exhausts air fowardly through a front mounted exhaust filter.